As a glider pilot and tow pilot, there are a couple of SSA - recommended hand signals/procedures that I find confusing at best and dangerous at worst:

First, the HOLD and STOP signals. Used interchangeably by most wing runners, the HOLD signal (arms level) is essentially invisible from the towplane, and impossible to do if holding a wing level (as with water ballast). Think about it - looking aft from the towplan, you have a bunch of horizontal features (horizon, wings, tail, etc) competing with the wing runners arms. In addition, the internationally (civilian and military) agreed use of that signal is to direct a helicopter to hover! Instead, why not use the unniversally recognized (and previous SSA signal - check an old copy of Joy Of Soaring) signal of an arm held vertically, palm forward? This is easy to see from the towplane, is distinct from the "take up slack" waving of the arm (can be timed to stop the towplane precisely), and can be done one handed. With the addition of a hat in the hand it is even easier to see from the towplane.

The SSF "STOP" signal is even dumber - totally invisible from the towplane and not used anywhere else that I can find. And again is a two handed signal.

I propose that the SSA and SSF change the US standard signal for HOLD and STOP to one arm held straight up (preferable with a hat or paddle), or two arms held up crossed (if both arms are free).

Second, I think there needs to be additional emphasis that the wing runner is NOT TO GIVE THE "BEGIN TAKEOFF" SIGNAL UNTIL THE GLIDER PILOT WAGS HIS RUDDER! I would even suggest that the "BEGIN TAKEOFF" signal SHOULD NOT BE DONE BY WING RUNNERS.